Exhaled Carbon Monoxide (eCO) for Diffusing Capacity (DLCO) Correction

The purpose of this study is to check the accuracy of a procedure called exhaled carbon monoxide (eCO) testing. Exhaled carbon monoxide is used by physicians to help assess breathing in people with conditions like asthma and emphysema. 100 subjects who are at least 18 years of age will be invited to participate. The first 50 subjects (Part 1) must have had pulmonary function testing (spirometry, diffusing capacity and CO-oximetry) for clinical reasons ordered by their own physician in order to enroll. The second 50 subjects (Part 2) may undergo this testing as part of the study. Participation requires 1 visit, during which subjects will undergo breathing tests, have blood collected, and answer 3 questions. The number of breathing tests will depend on which part of the study subjects are in. Subjects participating in Part 1 of the study will undergo 2-4 additional diffusing capacity (breathing) tests. (Clinical tests require 2-4 tests. This study requires 6. The number of research tests done depends on the number of clinical tests done. Subjects participating in Part 2 of the study who have not had clinical breathing tests ordered by their physician will undergo 1 spirometry (breathing) test (3-8 blows into a tube), 6 diffusing capacity (breathing tests), and blood draw. All subjects will undergo eCO testing (blowing into a machine) before the breathing tests and after the breathing tests. The visit in Part 1 of the study will take about 30 minutes. The visit in Part 2 of the study will take about 30 minutes for subjects who have undergone clinical breathing tests recently, and about 1 ½ hours for those who must undergo breathing tests for the research. Subjects will also have their pulse oximetry (using a standard finger clip) performed at the same time as each eCO testing.